Let's start with the first serial port on pins 1&2, this is addressed as Serial1, so Serial1.begin(11520); works.
Likewise for the second serial port on pins 7&8, this is addressed as Serial2 and Serial2.begin(11520); works.
I am sure you get the...
Could you explain what you mean by the above sentence. I think I know what you mean, but we have a large number of members who DO NOT have English as a first language and may not understand your sentence, especially the halts the Teensy inviting...
Personally I would use OLED screens such as this. Square ones are available a little cheaper. They are driven by I2C which is slower than SPI, but I suspect that speed is not a priority as they will (I guess) not be changed very frequently...